Negative voltage regulator.

Main Question or Discussion Point

So for a power supply project I need a voltage regulator giving me a positive output at around 40v.
Obsessively you can not buy these, So i am useing a circuit which consists of a resistor, npn transistor, and zener diode. the positive input goes to the collector of the transistor and through the resistor to the base of the transistor, and a zener diode of 39v is on the base to ground. Then my output is the emitter. This works fine, but...

As some of you may know I do a lot in audio and need a negative voltage regulator for the split audio power supply, is there a modification I need to do to make this the same thing just as a negative voltage regulator?

Also what the heck does a negative voltage regulator do anyway? I understand a positive obsessively but am not sure about the negative.

negative voltage regulators regulate a negative voltage relative to ground. -40V in, -12v Out, for example. You can't just hook -40V into a positive regulator. (can't take the input below ground without destroying it --- look at the absolute max specs for the input voltage range)

You didn't say 3 amps. Any other secret specifications?
Using a zener diode and emitter follower is sloppy. google "lm317 current booster" for a better controlled supply architecture. You can use any regulator. I'll let you figure out the negative supply stuff.

The Negative regulated power supply provides for the negative half cycle of a the audio sine wave. It is typical for audio amps to be powered by positive and negative supplies to produce high fidelity reproduction.
An LM723 is typically a 10 pin positive regulator with an output current of 150mA...it is used with lots of peripheral components to make fine precision power supplies.
If you have a solid dc source that provides +40V and -40V with respect to common you can use positive and negative 3 terminal regulators with some peripheral components to provide the voltage and current that you need.